Apparatus for producing ground and polished glass strip



Fab. 10, "1942. F. EWALDRON a-rm. 2 5

APPARATUS FOR PRODUCING GBQUND AND POLISHED GLASS STRIP Filed March 13, 1939 5 F/qJ. a I a I 3 O O 4" Patented Feb. 10, 1942 APPARATUS FOR PRODUCING GROUND AND POLISHED GLASS STRIP Frederic Barnes Waldron, Prescot, and James Harris Griflin, St. Helens, England, assignors to Pilkington Brothers Limited, Liverpool, England, a British company Application March 13, 1939, Serial No. 261,538 In Great Britain March 31, 1938 3 Claims. (01. 51-110) This invention relates to an apparatus for producing a ground and polished strip of glass from a supply of molten glass, and has for its object means for shaping the edges of the strip.

The apparatus to which the invention relates comprises a furnace for the supply of molten glass, a strip-forming machine adapted to form a strip from the molten glass, a leer and a grinding and polishing machine in which disc tools rotating on axes perpendicular to the surfaces of the strip operate simultaneously on both sides of the strip.

The edges of the strip are liable to curl, so that they project generally above the upper surface of the strip, but sometimes below the lower surface. The first grinding tools are liable to break the strip at the projecting edges, before they have ground them down to the general level of the strip.

The projecting edges may be removed by cut ting off narrow strips from the strip, before it enters the grinding apparatus, but it is then found that the sharp rectangular edges which are left cut or scrape the felts of the polishing tools.

According to the invention, grinding apparatus is provided to operate on the edges of the strip in a position before the polishing apparatus to grind surfaces on the edges of the strip which meet the surface of the strip at an angle substantially greater than a right angle, measured through the substance of the strip. When the strip formed has edges which curl so as to project beyond the general plane of the strip surface, preliminary grinding apparatus is provided in a position before the grinding apparatus, to operate on the edges of the strip to grind away the projecting portion of the curled edge substantially to the plane of the strip surface, and further grinding apparatus to operate on the corners of the edges formed by the preliminary grinding apparatus.

In the accompanying drawing:

Figure 1 is a diagrammatic part plan view of a polished strip making apparatus;

Figures 2' and 3 are sections of two forms of edge portion of the strip;

Figure 4 is a view looking in the direction of the strip of a pair of edge grinding devices;

Figure 5 is side View of the devices shown in Figure 4 Figure 6 shows a grinding wheel operating on curled edge, and

Figure 7 is a section similar to those of Figures 2 and 3.

Referring to Figure 1, molten glass I issues from the tank 2 and is formed into a strip 3 by the rolling apparatus 4. The strip passes through a leer 5 and then to a grinding apparatus of which the first and last grinding tools 6 are shown and then to a polishing apparatus of which the first polishing tool I is shown. Similar tools immediately below the tools 6 and I operate simultaneously on the under surface of the strip 3. Before the strip 3 reachesthe grinding apparatus, the four corners of its two edges are ground by wheels 8.

The case will first be described in which the edges of the strip are out off as the strip 3 issues from the leer 5, leaving the strip 3 with a rectangular edge 9 as shown in Figure 2, with'sharp corners shown in dotted lines at II]. If such a strip be passed through the grinding apparatus, it is reduced in thickness to the dotted lines II, the corners at the edge still remaining sharp. When such a strip with sharp corners passes into the polishing apparatus, the sharp corners out or scrape the polishing felts, and injuriously affect the polishing operation. According to the invention, the sharp corners ID are ground'away, leaving surfaces l2. which meet the surfaces of the strip at an angle I3 which is substantially greater than a right angle. The angle shown on the drawing, is and this is found to be satisfactory in causing no injury to the polishing felts. The surfaces [2 must be ground to a depth sufficient to bring them below the planes indicated by the dotted lines H so that a portion of each surface I2 remains below the level of the surface of the polished strip, that is to say, the surface of the ground strip indicated by the lines H.

Figures 4 and 5 show a pair of grinding de-, vices, as indicated at 8 in Figure 1, operating on the two corners of one edge of the strip 3. Motors [4 are mounted on slides [5 on a frame l6, and carry face grinding wheels ll. The motors [4, with wheels H, can be advanced towards the edge of the strip 3 by screws l8, and they are set on the frame l6 at an angle such that they grind surfaces I2 (Figure 2) at the desired angle.

Next, the case will be described when the edges of the strip are not cut. The form of the edge of the strip is then generally as shown in Figure 3, following the dotted line I9, which shows a curled edge. If a strip of this form is passed into the grinding apparatus, the grinding tools 6, coming into contact only with the projecting portions 19 are liable to break the strip before they have ground the projecting portions away and rest on the whole surface of the strip.

A grinding device, such as the motor [4 with face grinding wheel 11 is then set as shown in Figure 6 (in which only the wheel I! is shown) so as to grind away the projecting portion l9 substantially to the line 20, that is, to the plane of the surface of the strip. The surface so ground is conveniently at a very small bevel. The surface so ground leaves a corner 2| which is generally nearly a right angle, and is therefore liable to injure the polishing felts. A second grinding wheel therefore is operated to grind away the corner 2| and form a surface I 2, as in the case shown in Figure 2. The grinding wheel operating to form the surface 12 may operate first, thus grinding away a portion of the projection I9, and the other grinding wheel operating to form the surface 20 may follow it. The underside of the edge is curved and presents no sharp corners even after passing through the grinding apparatus and consequently need not be ground. Sometimes the curl of the edge is downwards, and in this case the grinding wheels operate on the lower surface and corner.

Alternatively, the projection 19 may be ground away to form a surface 22 (Figure '7) which extends to a level below that of the plane H to which the strip is ground in the grinding apparatus. This, however, entails more grinding work than does the formation of the two surfaces 29 and I2 of Figure 3.

When the strip has a curled edge, the grinding device which operates to grind away the projecting portions of the edge must be placed before the grinding apparatus, as at 8 in Figure 1. The grinding devices which operate to form the surface l2, whether on a strip with cut edge, or on a strip from which the projecting portion of a curled edge has been cut away, are most conveniently also placed before the grinding apparatus, but they may be placed at any point before the polishing apparatus. If they are placed at or near the end of the grinding apparatus, less glass has to be ground away to form a sur face l2 which extends to a level below the surface of the polished strip.

Having described our invention, we declare that what we claim and desire to secure by Let-- ters Patent is:

1. In an apparatus for grinding and then polishing a strip of glass comprising a series of rotating disc grinding tools arranged in advance of a series of rotating disc polishing tools operating on and supporting the lower surface of the strip and similar series of rotating disc grinding and polishing tools operating on the upper surface of the strip, each tool being opposite to a lower tool, and pairs of rollers adapted to grip the strip and drive it between the tools, the combination of face grinding wheels for grinding the edges of the strip, arranged in advance of the first polishing tool of the series, the operative face of each wheel being in a plane making an angle less than 35 degrees with the plane of the strip, supports for the face grinding wheels, and adjusting means on the supports to adjust the position of the wheels relatively to the strip, each face grinding wheel being arranged to contact with the edge of the strip along a line extending beneath the level of the surface of the finished strip.

2. In an apparatus for grinding and then polishing a strip of glass comprising a series of rotating disc grinding tools arranged in advance of a series of rotating disc polishing tools operating on and supporting the lower surface of the strip and similar series of rotating disc grinding and polishing tools operating on the upper surface of the strip, each upper tool being opposite to a lower tool, and pairs of rollers adapted to grip the strip and drive it between the tools, the combination of two face grinding Wheels for grinding each of the edges of the strip, arranged in advance of the first polishin tool of the series, one adapted to grind the upper cornerof the edge and the other the lower corner, the operative face of each wheel being in a plane making an angle less than 35 degrees with the plane of the strip, supports for the face grinding wheels, and adjusting means on the supports to adjust the position of the wheels relatively to the strip, each face grinding wheel being arranged to contact with the edge of the strip along a line extending beneath the level of the siu'face of the finished strip.

3. In an apparatus for grinding and then polishing a strip of glass comprising a series of rotating disc grinding tools arranged in advance of a series of rotating disc polishing tools operating on and supporting the lower surface of the strip, and similar series of rotating disc grinding and polishing tools operating on the upper surface of the strip, each upper tool being opposite to a lower tool, and pairs of rollers adapted to grip the strip and drive it between the tools, the combination of face grinding wheels for grinding the edges of the strip arranged in advance of the first grinding tool of the series, the operative face of each wheel being in a plane making an angle less than 35 degrees with the plane of the strip, and arranged to contact with the edge of the strip along a line extending beneath the level of the surface of the finished strip, two auxiliary face grinding wheels arranged in advance of the said face grinding wheels, one at each edge of the strip and on a side of the strip which presents a curled edge, the operative face of each auxiliary grinding wheel being in a plane making an angle less than 10 degrees with the plane of the strip,.supports for the face grinding wheels, and adjusting means on the supports to adjust the positions of the wheels relatively to the strip.

FREDERIC BARNES WALDRON. JAMES HARRIS GRIFFIN. 

